For the inner liner disposed as an air barrier layer on an inner surface of a tire for maintaining internal pressure of the tire, a rubber composition mainly made of butyl rubber or halogenated butyl rubber is commonly used. However, since the rubber composition mainly made of the butyl rubber has a low air bather property, the inner liner using such a rubber composition needs to have a thickness of around 1 mm.
On the other hand, ethylene-vinyl alcohol copolymer (hereinafter, it may be abbreviated as EVOH) is known to have an excellent gas barrier property. Since an air transmission amount of the EVOH is hundredth part or less than that of the rubber composition used for the butyl-based inner liner described above, an inner liner made of EVOH with a thickness of 100 μm or less may significantly improve internal pressure retention of the tire. The inner liner made of EVOH with the thickness of 100 μm or less is usable and hardly breaks or causes cracks due to bending deformation at the time of tire rolling. Hence, it may be said that, in order to improve the internal pressure retention of a pneumatic tire, it is effective to use EVOH for the inner liner of the tire. Patent Document 1, for example, discloses a pneumatic tire comprising an inner liner made of EVOH.
However, when normal EVOH is used for the inner liner, while it is very effective in improving the internal pressure retention of the tire the inner liner made of EVOH has been broken or causing cracks due to deformation during bending due to its elastic modulus significantly higher than that of rubber commonly used for the tire. Thus, when the inner liner made of EVOH is used, although the internal pressure retention of the tire before use of the tire is greatly improved, a used tire subjected to bending deformation during tire rolling sometimes has the internal pressure retention lower than that before use.
Accordingly, development of an inner liner that has high crack resistance while maintaining the gas barrier property and allows a reduction in thickness has been desired. To that end, it is considered to use a laminated product in which an elastic film or a sheet with excellent crack resistance and a resin film with excellent gas barrier property are joined to each other and integrated. In such a case, since the elastic film or the like is contained in the laminated product, it becomes a question whether an excellent gas barrier property may be achieved. Further, when the laminated product is used as the inner liner, improvement in fatigue resistance to be durable for a prolonged use has been desired.